Yeasts & Fermentation Flashcards
Who discovered yeasts, when?
Louis Pasteur (Circa 1860)
What are the favourable conditions for yeasts?
12-30degrees c
What are some unfavourable conditions for yeasts in the fermentation process?
- High acid
- Too much alcohol
- Lack of oxygen
- Extreme temperatures
What is pied de cuve?
Already-fermenting wine that can be used to kick-start the fermentation process
In what situations would you need to add yeast?
- When rain fall has been substantial prior to picking
- If you want more control over the alcoholic fermentation
- If you want to ensure that fermentation reaches its full course
- If you want to raise alcohol content
- If you want to make a sparkling wine
In what forms can you buy yeast?
- Diluted slurry
- Cake
- Gelatin sheets
- Dried
- Freeze dried
What are some examples of features of lab-made yeasts?
- Resist higher alcohols
- Alcohol yield
- Ability to bring out certain aromas
- Tendency to produce lower levels of acetic acid and ethyl acetate
At what temperature does yeast completely die?
-20c
At what percentage of sugar in the must does fermentation slow and then halt?
Slows at 30%, halts at 60%
Why do high levels of tannins slow the fermentation process?
They stick to the yeast membrane
At what ABV do natural yeasts tend to die?
15-15.5%
How much CO2 is produced from 1hL of must?
4.5hL
What is the most widely used strain of lab made yeasts?
Saccharomyces
What are 3 features of lees contact?
- Higher acid
- More texture
- Complexity of aromas (brioche, toast, bread, butter)
What is the definition of alcoholic fermentation?
The transformation by yeasts and sugars contained in grape must into ethyl alcohol and carbon dioxide
